In the context of economic inequality, gender gap
generally refers to the differences in the wages of men and women. There is a debate to
what extent this is the result of gender differences, lifestyle choices
(e.g., number of hours worked), or because of discrimination.

Statistics

A United Nations report found that women working in manufacturing
earned the following percentages in relation to men in 2003. The
statistics are based on wages for all male and female workers,
regardless of age, experience, or other factors. The report states:
"International comparisons of wage ratios presented here must be
made with great caution. The coverage, definitions and methods of
compiling wage statistics differ significantly from country to
country. [...] Furthermore, earnings are very much dependent on the
number of hours worked, and where female workers generally work a
much smaller number of hours than male workers, this factor must be
kept in mind when interpreting the wage ratio."

United States

In 2004, women's wages in the USA were 76.5% of men's wages.
David R.Hekman and colleagues (2009) found that
customers prefer white men over equally-well performing women and
minority employees, which may help explain why white men continue
to earn more than other types of employees.

Hekman et al. (2009) found that customers who viewed videos
featuring a black male, a white female, or a white male actor
playing the role of an employee helping a customer were 19% more
satisfied with the white male employee's performance and also were
more satisfied with the store's cleanliness and appearance. This
despite that all three actors performed identically, read the same
script, and were in the exact same location with identical camera
angles and lighting. Moreover, 45 percent of the customers were
women and 41 percent were non-white, indicating that even women and
minority customers prefer white men. In a second study, they found
that white male doctors were rated as more approachable and
competent than equally-well performing women or minority doctors.
They interpret their findings to suggest that employers are willing
to pay more for white male employees because employers are customer
driven and customers are happier with white male employees. They
also suggest that what is required to solve the problem of wage
inequality isn't necessarily paying women more but changing
customer biases. This paper has been featured in many media outlets
including The New York Times,
The Washington Post, The Boston Globe, and National Public Radio.

Debate

However, some groups, such as the Independent Women's Forum, argue
that the wage gap does not exist. For further information, see
Male-female
income disparity in the USA. Similarly, Thomas Sowell argued in
the book, Civil Rights, marriage is the main variable
driving the wage gap--that married women make less than other types
of workers.

According
to the Centre for Economic Performance (CEP) at the London School of
Economics, it would take 150 years for the income gap between
the two genders to close up due to discrimination and ineffective
government policies. However this study did not compare
equal jobs or conditions, rather the total earnings only and is
generally considered to be an unrealistic comparison.